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What's the difference between linear power supply and switch power supply?
Chandra Ganeshan, Built many circuits in the field of Power Electronics Updated Jan 5
Why is a linear power supply called "linear"?
Weight of the transformer is Inversely Proportional to frequency. This is the
What are the difference between SMPS and UPS?
crucial factor which led to the invention of the SMPS. To know the difference
What is SMPS?
between Linear power supply and SMPS read below. Long time ago when a DC power supply is required AC-DC converter is made with the help of Step Down Transformer(50Hz/60Hz) followed by a Bridge-
What are the differences between SMPS and normal power supplies? What is the difference between charger and SMPS?
Rectifier circuit and then a Voltage Regulator IC. But all modern AC-DC converter only contains SMPS circuit(Mobile/Laptop Charger, Circuit powering CPU etc.,)
What is the difference between a power transformer and a distribution transformer? What are the pros and cons of linear versus switch-mode power supply?
So what happened to the Linear power supply, Here comes the actual advantages and disadvantages. Upvote · 12 Share
Ask New Question More Related Questions
Although Linear power supply were able to provide the requirement of AC-DC conversion. The circuit is very very bulky and adds to weight. This is because of the fact that it uses a 50/60 Hz transformer. Remember, as i said weight of the transformer is inversely proportional to frequency. So scientists were trying to reduce the weight of the AC-DC circuit to make the charger more portable and easy to handle. For this they need to Increase the Frequency so as to bring up a decrease in weight. But these normal transformer (50/60Hz Tranformer) cannot work at higher frequency. So a specially made transformer which can work at higher frequency were made called Switch Mode Transformer. It can handle frequency of about 50 KHz to 1MHz. So that’s how scientist reduced the weight of the AC-DC circuit. So is that all the difference between Linear and SMPS circuit? The answer is No. Another major aspect about Linear power supply is that they are open loop circuit, meaning they do not employ any feedback mechanism to control output voltage. Suppose for example you buy a Linear charger in Asia(AC supply voltage in ASIA-240 Volts) which outputs 5 Volt DC. Imagine If you are going to connect this charger in U.S.A.(AC supply voltage in U.S.A - 110 Volts). It will not provide the same output voltage 5 Volt D.C. It will be lesser than 5 Volt D.C. As you can observe the fact that it does not employ any control mechanism to control its output to same 5 Volt, when the input supply voltage changes. On the other hand, imagine you are buying the Same charger in Asia. But this time you are buying a SMPS charger instead of Linear charger. And if you connect the SMPS charger to U.S.A. The output of SMPS will be 5 Volts even with the reduced input voltage. This is because of the Feedback mechanism in the SMPS. Stop reading if you are bored here. Go ahead if you wanna know more! So Lets go to the circuit inside Linear and SMPS circuit. Linear Power Supply:
As you can there is 50/60 Hz transformer at the input followed by Bridge Rectifier followed by the Regulator. So Lets say the Input Voltage decreases to about 110 Volts from 240 Volts. The output of the Transformer will decrease to nearly half . So instead of outputting 5 V AC it will now output 2.5 Volt approximately so this will be converted to DC by the bridge rectifier and finally after regulation you will end up with just 2.5 Volt DC or even lesser. This is a major disadvantage to the equipments that we connect to this charger. So lets see how it is overcome in SMPS circuit. Switched Mode Power Supply:
So here the Input voltage at 240 Volts at 50/60Hz frequency is first fed to Input Rectifier stage, Which converts 240 Volt AC to 240 Volt DC. This 240 DC voltage is fed to a High Frequency Switch which converts this DC to High Frequency AC at 240 Volts with a frequency between 50KHz to 1MHz, as mentioned in the circuit. So now we have 240 Volt AC at a higher frequency. Here comes the Switched Mode Transformer. These Switched Mode Transformer(SMT) are capable of handling higher frequency. So this SMT will now step down the 240 Volt AC at Higher frequency to required Output AC voltage at higher frequency. And the output AC voltage is now converted to DC using output rectification and filtering circuit. The DC output voltage is fed back to the control circuit which gives the firing pulse for the High Frequency Switch. Thus achieving AC to DC conversion So coming to the example, If you connect the SMPS charger in U.S.A. Lets see what happens. Input voltage will be 110 Volts and the Input DC rectification circuit will convert this 110 Volt AC at 60Hz to 110 Volt DC and the High frequency Switch will convert this 110Volt DC to 110 Volt AC at Higher Frequency(110 Volt AC with frequency between 50 kHz and 1MHz). The SMT will step down this voltage to the required value which will be converted to DC by the output rectification circuit. Here we will now have a reduced output DC voltage less than 5 Volts. But since it employs feed back mechanism. Feed back pulses will be sent to the control circuit of the High Frequency switch which will indicate that the output voltage is lesser than the required value. So the duty cycle of the firing pulse to be fed to the High frequency switch is increased and this increased on time of the switch increase the average voltage at the output and thus the duty cycle of the firing pulse is kept on increasing till the output voltage reaches 5 Volts. This is how the output voltage is adjusted even if the input voltage changes. This is the reason why you will see a label in the Laptop and mobile chargers indicating that it can work between in 100 Volts to 240 Volts as seen in the label below.
Due to these exemplary advantages SMPS is now used in all major circuit as it employs Closed Loop mechanism and also because of the fact that it is lesser in weight. On the other hand, due to heavy weight and Open Loop mechanism Linear Power Supply is not used anymore widely. There are also even more advantages for SMPS in the fact that SMPS have higher efficiency than Linear power supply. Whereas Linear power supply have lower efficiency dissipating major portion of energy as heat. The advantages of SMPS are unlimited! Questions are welcome! 945 Views · View Upvoters · Not for Reproduction
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Home
Linear Power Supply
SMPS
Answer
Spaces
Notifications
Related Questions
Electronics
What is the difference between linear power supply and SMPS I need a clear explanation? Follow · 1
Answer
Add Question or Link
Search Quora
What are the advantages of SMPS over other power supply? What are the advantages of SMPS compared to a linear power supply?
Request
1 Answer
What's the difference between linear power supply and switch power supply?
Chandra Ganeshan, Built many circuits in the field of Power Electronics Updated Jan 5
Why is a linear power supply called "linear"?
Weight of the transformer is Inversely Proportional to frequency. This is the
What are the difference between SMPS and UPS?
crucial factor which led to the invention of the SMPS. To know the difference
What is SMPS?
between Linear power supply and SMPS read below. Long time ago when a DC power supply is required AC-DC converter is made with the help of Step Down Transformer(50Hz/60Hz) followed by a Bridge-
What are the differences between SMPS and normal power supplies? What is the difference between charger and SMPS?
Rectifier circuit and then a Voltage Regulator IC. But all modern AC-DC converter only contains SMPS circuit(Mobile/Laptop Charger, Circuit powering CPU etc.,)
What is the difference between a power transformer and a distribution transformer? What are the pros and cons of linear versus switch-mode power supply?
So what happened to the Linear power supply, Here comes the actual advantages and disadvantages. Upvote · 12 Share
Ask New Question More Related Questions
Although Linear power supply were able to provide the requirement of AC-DC conversion. The circuit is very very bulky and adds to weight. This is because of the fact that it uses a 50/60 Hz transformer. Remember, as i said weight of the transformer is inversely proportional to frequency. So scientists were trying to reduce the weight of the AC-DC circuit to make the charger more portable and easy to handle. For this they need to Increase the Frequency so as to bring up a decrease in weight. But these normal transformer (50/60Hz Tranformer) cannot work at higher frequency. So a specially made transformer which can work at higher frequency were made called Switch Mode Transformer. It can handle frequency of about 50 KHz to 1MHz. So that’s how scientist reduced the weight of the AC-DC circuit. So is that all the difference between Linear and SMPS circuit? The answer is No. Another major aspect about Linear power supply is that they are open loop circuit, meaning they do not employ any feedback mechanism to control output voltage. Suppose for example you buy a Linear charger in Asia(AC supply voltage in ASIA-240 Volts) which outputs 5 Volt DC. Imagine If you are going to connect this charger in U.S.A.(AC supply voltage in U.S.A - 110 Volts). It will not provide the same output voltage 5 Volt D.C. It will be lesser than 5 Volt D.C. As you can observe the fact that it does not employ any control mechanism to control its output to same 5 Volt, when the input supply voltage changes. On the other hand, imagine you are buying the Same charger in Asia. But this time you are buying a SMPS charger instead of Linear charger. And if you connect the SMPS charger to U.S.A. The output of SMPS will be 5 Volts even with the reduced input voltage. This is because of the Feedback mechanism in the SMPS. Stop reading if you are bored here. Go ahead if you wanna know more! So Lets go to the circuit inside Linear and SMPS circuit. Linear Power Supply:
As you can there is 50/60 Hz transformer at the input followed by Bridge Rectifier followed by the Regulator. So Lets say the Input Voltage decreases to about 110 Volts from 240 Volts. The output of the Transformer will decrease to nearly half . So instead of outputting 5 V AC it will now output 2.5 Volt approximately so this will be converted to DC by the bridge rectifier and finally after regulation you will end up with just 2.5 Volt DC or even lesser. This is a major disadvantage to the equipments that we connect to this charger. So lets see how it is overcome in SMPS circuit. Switched Mode Power Supply:
So here the Input voltage at 240 Volts at 50/60Hz frequency is first fed to Input Rectifier stage, Which converts 240 Volt AC to 240 Volt DC. This 240 DC voltage is fed to a High Frequency Switch which converts this DC to High Frequency AC at 240 Volts with a frequency between 50KHz to 1MHz, as mentioned in the circuit. So now we have 240 Volt AC at a higher frequency. Here comes the Switched Mode Transformer. These Switched Mode Transformer(SMT) are capable of handling higher frequency. So this SMT will now step down the 240 Volt AC at Higher frequency to required Output AC voltage at higher frequency. And the output AC voltage is now converted to DC using output rectification and filtering circuit. The DC output voltage is fed back to the control circuit which gives the firing pulse for the High Frequency Switch. Thus achieving AC to DC conversion So coming to the example, If you connect the SMPS charger in U.S.A. Lets see what happens. Input voltage will be 110 Volts and the Input DC rectification circuit will convert this 110 Volt AC at 60Hz to 110 Volt DC and the High frequency Switch will convert this 110Volt DC to 110 Volt AC at Higher Frequency(110 Volt AC with frequency between 50 kHz and 1MHz). The SMT will step down this voltage to the required value which will be converted to DC by the output rectification circuit. Here we will now have a reduced output DC voltage less than 5 Volts. But since it employs feed back mechanism. Feed back pulses will be sent to the control circuit of the High Frequency switch which will indicate that the output voltage is lesser than the required value. So the duty cycle of the firing pulse to be fed to the High frequency switch is increased and this increased on time of the switch increase the average voltage at the output and thus the duty cycle of the firing pulse is kept on increasing till the output voltage reaches 5 Volts. This is how the output voltage is adjusted even if the input voltage changes. This is the reason why you will see a label in the Laptop and mobile chargers indicating that it can work between in 100 Volts to 240 Volts as seen in the label below.
Due to these exemplary advantages SMPS is now used in all major circuit as it employs Closed Loop mechanism and also because of the fact that it is lesser in weight. On the other hand, due to heavy weight and Open Loop mechanism Linear Power Supply is not used anymore widely. There are also even more advantages for SMPS in the fact that SMPS have higher efficiency than Linear power supply. Whereas Linear power supply have lower efficiency dissipating major portion of energy as heat. The advantages of SMPS are unlimited! Questions are welcome! 945 Views · View Upvoters · Not for Reproduction
Add a comment...
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